Studies of virus specific immune responses in HIV exposed and infected individuals as well as SIV vaccine studies in monkeys suggest that it is unlikely that vaccine approaches that stimulate a single arm of the immune system will provide effective protection from viral infection. Several studies have shown that strong CD8+ cytotoxic T lymphocytes (CTL) responses may be elicited by infection or vaccine candidates, which may correlate with marginal decreases in viral loads, yet these do not correlate with protection from infection or disease progression. However, In addition to CTL, B-lymphocytes also play an important role in the immune response to infection by secreting neutralizing and non-neutralizing antibodies to combat invading pathogens. There is evidence that HIV-1 impairs protective immunoglobulin G (IgG) and immunoglobulin A (IgA) responses against pathogens and vaccines by inducing progressive loss of these CD4+ T helper cells. The presence of low levels of memory B cells and defective naive B cells in HIV infected patients have also been reported. In summary, B cell dysregulation is likely to play a major role in the progression to AIDS in HIV-infected patients. If so, this in turn suggests that maintenance of normal humoral immune responses may be the key to preventing and controlling infection. HIV-specific mucosal IgA and systemic cellular responses in HIV protection have both been proposed to play a role in studies of discordant heterosexual couples. In addition, several new findings suggest SIV-specific IgA responses in mucosal and peripheral immune compartments are important in controlling viral infection. Recent reports have also shown that the specificity and quantitative properties of antibody binding to antigen plays an important role in determining the neutralizing activity of the antibody. Thus we hypothesize that differences in the quality of antigen specific immunoglobulin (Ig) responses will be observed in animals in which viral loads are reduced or undetectable compared to animals that have persistent viremia and progress to AIDS. We also hypothesize that the level of antigen-antibody binding properties and antigen-specific effector memory B cells in tissues or secretory Ig will correlate with the reduction of viral load or disease progression in SIV infected macaques. In the proposed studies, we will examine and compare SIV-specific IgA, IgG and IgM immune responses and antibody binding properties in peripheral blood, and mucosal secretions of macaques inoculated with SIVmac251 and/or SHIVsf162p3. We will also examine the effector function of memory B cells in peripheral blood, broncho-alveolar lavage (BAL), bone marrow (BM), small intestine and lymph node tissues from SIV infected macaques. The specific aims are: Specific Aim 1: To compare the role of antigen specific IgA, IgG and IgM immune responses in macaques with different levels of immunity to SIV/SHIV infection. We will compare antigen specific IgA, IgG and IgM responses in macaques intravenously, intravaginally, and intrarectally inoculated with SIVmac251 (a highly pathogenic virus that consistently results in persistent viremia and AIDS). Antigen specific immunoglobulin responses will also be assessed in SIVmac251 and SHIVsf162p3 inoculated macaques which are able to control their infection and become long-term nonprogressors (LTNP). We will also be able to identify major IgA, IgG and IgM specific B cell epitopes and their role in differentiating the immune responses of SIV inoculated protected and unprotected macaques. Specific Aim 2: To determine the kinetics of antibody binding properties in macaques with different levels of immunity to SIV/SHIV infection. We will also compare quantitative and qualitative binding properties of all longitudinal plasma/serum samples and/or mucosal secretions from macaques with different levels of immunity to trimeric recombinant SIV/SHIVgp140 envelope proteins using surface plasmon resonance (SPR) technology (Biacore). We expect that a difference in the quality of antibody population might exist in macaques which are able to control viremia compared to those that rapidly progress to AIDS. Specific Aim 3: To quantify effector memory B cells in macaques infected with SIV by different routes of inoculation. We hypothesize that mucosal immune responses may differ depending on the route of inoculation. Thus, effector memory B cells will be evaluated and quantified in different tissues including peripheral blood, intestines, lymph nodes, BM, and BAL samples of intravenously and mucosally inoculated macaques. We will also quantify secretory IgA and IgG from both systemic and mucosal immune sites. Using this approach, we predict that we will be able to correlate SIV specific mucosal immune responses with reduction of viremia and protection from disease progression in macaques infected with pathogenic viruses. PUBLIC HEALTH RELEVANCE: Studies of virus specific immune responses in HIV exposed and infected individuals as well as SIV vaccine studies in monkeys suggest that it is unlikely that vaccine approaches that stimulate a single arm of the immune system will provide effective protection from viral infection. Several studies have shown that strong CD8+ cytotoxic T lymphocytes (CTL) responses may be elicited by infection or vaccine candidates, which may correlate with marginal decreases in viral loads, yet these do not correlate with protection from infection or disease progression. However, In addition to CTL, B-lymphocytes also play an important role in the immune response to infection by secreting neutralizing and non-neutralizing antibodies to combat invading pathogens. B cell dysregulation is likely to play a major role in the progression to AIDS in HIV-infected patients. If so, this in turn suggests that maintenance of normal humoral immune responses may be the key to preventing and controlling infection. Thus we hypothesize that differences in the quality of antigen specific immunoglobulin (Ig) responses will be observed in animals in which viral loads are reduced or undetectable compared to animals that have persistent viremia and progress to AIDS. We also hypothesize that the level of antigen-antibody binding properties and antigen-specific effector memory B cells in tissues or secretory Ig will correlate with the reduction of viral load or disease progression in SIV infected macaques. In the proposed studies, we will examine and compare SIV-specific IgA, IgG and IgM immune responses and antibody binding properties in peripheral blood, and mucosal secretions of macaques inoculated with SIVmac251 and/or SHIVsf162p3. We will also examine the effector function of memory B cells in peripheral blood, broncho-alveolar lavage (BAL), bone marrow (BM), small intestine and lymph node tissues from SIV infected macaques. Using this approach, we predict that we will be able to correlate SIV specific mucosal immune responses with reduction of viremia and protection from disease progression in macaques infected with pathogenic viruses.